I know there is a ton of threads out there that debate 2 bolt vs 4 bolts vs splayed caps... I am in the middle of my 383 stroker build and what to get some input on my specific build. I have a couple of blocks laying around including 4 bolt and 2 bolt mains but I decided to use a two bolt main because it was already set up for a roller motor. After a month of going back and forth it has come time to make the decision to splay cap the block or leave it a two bolt main (studed) here are the stats.... 383 stroker, forged eagle crank, forged scat 5.7 rods, probe -22 dish forged pistons, vortec iron heads (906 casting, all new springs and valves machined for up to .600 lift), comp cams mutha thumper camshaft 291, performer intake, elderblock 750 cfm carb. End compression ratio after decking should be around 9.8-10 to 1. It is going in my 53 Chevy pickup and will probably only see the strip a few times in its life... but I do have a tendency to have a lead foot on the take off. Should I splay the caps or would it be a waste of my money? Thanks for the input.... and let the debate begin!
built a .30 over 355 with a cast crank and two bolt mains,using arp studs that i sprayed with a 500 hp port nitrous system for years.in a mud racer ,not a street car ,but you should be fine with either setup.
The pictures I've seen (never seen it in person) have blown out a cap because the failure of the bridge which I don't see how that has anything to do with more bolts. Now I've seen crank walks cause bearing failure but again im only a amature at best so that's why im asking the guys with more experince.
ran a 2 bolt main 355 with 1 rebuilt rod for 3 years on a dirt track, still running, in my drag car now, the motor was built in the 80's... we'll see how long it stays together....
I ran a dirt modified with a 377 motor for 5 years with a 2 bolt, 7200 all day long. 15 to 1 compression.... What you need to do is stake the main caps after they are torqued so they cannot walk.
Anything over 500 hp, & I'd go with a splayed 2-bolt. All the Sprint run that set-up, they're pushing way more horsepower. I run a standard 4-bolt in my street stock circle tracker, but I'm probably not even 375 hp...
Its like painting the inside of the engine -- not nessasry, But tell everybody you did it and your golden.
lol to dreracecar. Good looking out. Ricks Garage, first time I have heard of "staking the main caps", what exactly is this?
I've had a couple reputable engine builders tell me a cast crank/2bolt set up is good to 650hp. One of them won't use a 4bolt because of the meat it takes out of the web, and he builds winning round track motors.
4-Bolt !! 2-Bolt !! Mo-bolt !! They all can break when you put too much Horse-Power on top of em. This just ripped all the caps out of the block !!! Caps were in fine shape and hell the bearings even still look good !!! Nuff Said !!!! >>>>.
you dont really wanna rev that 383 often enough or high enough to need splayed caps.....run roundy pounders 2 bolt cast crank 355 all season hundred lap mains to 7500 and they last fine.....
2 bolt block is fine, hope its a 638 roller block. the 880's have a shorter cylinder length, they work fine but for a engine you want to see high mileage a 638
Thats the winning info. I also did same. Only if your going drag racing at above 8000 rpm should it be of any real help to have 4 bolt mains. But you motor dose need to be in balance in any case.
It does and doesn't. More bolts is not the cause, but can contribute to the destruction. The two things that will pretty much pull the main webbing or split the block is the crank flexing, and undampened harmonics induced into the block. You can do a few things to help remove some flex from the crank, one would be to use a quality steel crank, two would be to make sure it is truly zero balanced, and three to make sure to use a quality elastomeric harmonic balancer such as an ATI unit. But even then if the crank twists beyond a set point it will still bend. As for the block, there really isn't anything you can do to it. Either replace the block with one with thicker main webs, or one made from aluminum. Lifter valley braces don't do anything, and girdles just help contain the mess, and possible saves you an oil pan. What causes the block to be ripped apart is the bending of the crank, it pulls on the main webs. Being cast iron it can only flex so much, it eventually fatigues, fractures, cracks, and fails. Adding more of a clamp load is not going to do anything, because that's not the problem, its the harmonics that eventually shake the block apart. Start adding more bolts for more clamp load, all you really are doing is weakening the block by removing material in a critical area.
forged eagle crank, forged scat 5.7 rods, probe -22 dish forged pistons You don't really need the forged stuff for your application. But since you have it, I'd put in the splayed center caps to balance it all out should plans change down the road.
I was under the impression that the early (68-72) 4 bolts had the "good" nickle caps and blocks and the later versions were less nickle or some such story. Comments? And my O/T driver has a 388 and I had to go through 5 blocks to finally get a decent builder. Several had cracks in the main webbing and several would not clean up at .060! I promise that next time I will buy a new SHP or such as after adding up the cost of the "good used engines" and the machine shop vatting, boring, etc. I could have bought a new one and built a 427" for the same money, just saying, find a good machinist and double check everything, with out a good foundation, you have nothing. In the end the last block that was acceptable was a 1971 4 bolt out of a station wagon that was "low mileage" and it took a .060, go figure!?
Nothing to do with "Mains" but thats some serious Duration on that cam on the table!! Dam, lobes look square!!lol JimV PS must be for a "2 cyl"!!
I used to twist up 2-bolt main 350s to 7K in stock cars. They were claimers, so cheap, cheap, cheap was the order of the day. Never had a problem with it. Bob
Damn man. That is a crazy break down. Thanks for all your advice guys. I need to check my block numbers and see if its a 638, not sure.
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